95 Talon 420a motor, checked all obvious (tested 3 different pefectly working IAC's, no vacuum leaks, prefect compression, tested another working ECU)No engine codes other than for the IAC (code 25)
Problem:

Cold Start (open loop)- idles normal from 1000 rpm and drops to about 800 after a minute
Normal operating temp (closed loop) - idle jumps up to 1500 and revs up to 2000 than back to 1500 up and down and will not stop surging.

Hot Start - idle jumps to 4000rpm and bounces around between 3000 and 4000 idle seems to hang Than it surges between 2000 - 2500

My thoughts
When you start them motor cold it is in open loop.. (no feedback from sensors). When it gets to its normal operating temp the system goes into closed loop and gets its feedback from the sensors. So obviously I have a sensor problem or a wiring problem or something wrong in the IAC circuit (but the IAC is good, ECU is good)

Any help would be great !!! Thanks

IAC could be good itself, but the wiring could be F'd up.

EDIT: Have you checked the obvious section of wires around the EGR Pipe to make sure nothing has melted?

Originally posted by eclipse982nrRST
EDIT: Have you checked the obvious section of wires around the EGR Pipe to make sure nothing has melted?

I had a similar problem, and thats exactly what happened. I no longer have an EGR system just because of that